1. Field of the Invention
This invention relates to new water-soluble zwitterionic polymers which show high compatibility with anionic and cationic surfactants and good hair-softening and style-holding properties and to their use in hair treatment preparations, more especially in shampoos.
2. Statement of Related Art
Zwitterionic polymers are distinguished by the fact that they contain anionic groups, mostly carboxyl groups and quaternary ammonium groups in the molecule. Numerous zwitterionic polymers are known. It is also known that zwitterionic polymers can be used in hair treatment preparations. U.S. Pat. No. 3,836,537 describes the use of polymers of zwitterionic monomers in hair-setting preparations. The use of copolymers of dimethylaminoethyl methacrylate, acrylic acid and methyl methacrylate in hair-setting preparations and shampoos is described in U.S. Pat. Nos. 4,237,253 and 4,324,780. Zwitterionic copolymers of monomers containing quaternary ammonium groups and monomers containing carboxyl groups are disclosed in U.S. Pat. Nos. 4,544,240, 4,460,477, 4,484,631, 4,510,059 and 4,533,708, where such polymers are recommended as scale and corrosion inhibitors.
The zwitterionic polymers normally used for hair treatment and hair setting preparations have the disadvantage, particularly in formulations containing anionic surfactants, that the hair-softening and hair-setting properties are gradually lost in the event of prolonged storage. Purely cationic water-soluble polymers have the disadvantage that the hair-setting and style-holding properties are not sufficiently pronounced. Accordingly, there is a need to find hair-setting and hair-softening components for hair-treatment preparations, more especially for hair-care and hair-washing preparations, containing anionic surfactants which retain their effect even in the event of prolonged storage in the formulation.